Could use a pointer... or two

[Greek Acrobat]

Hi, I'm new here. In fact I'm new to electronics - the first time I opened up a pedal was 2 weeks ago. Please be gentle  :wink:

Anyhoo, my Russian Big Muff has stopped working - when I turn it on the signal just cuts out. I bought a multimeter today and I was wondering if someone could give me some pointers on how to go about testing the circuit to find the problem??

Cheers,
Paul.

[Rodgre]

obvious question.... the battery is okay? If there's NOTHING at all, the FIRST thing I would check is whether the circuit is getting power. If all the wires to the power supply or battery are intact, you might just want to put the meter on the circuit board where the positive power goes, and the black meter probe to ground (maybe the input jack's ring?)

If there is power, then I would check the switch itself. It's possible the switch could be dead. If you need to check that and you're not sure what lug is what and how to do a continuity test on it, you can cheat and tack solder a wire from the input jack right to the board and from the board right to the output jack. Hey, you just bypassed the bypass! ba-dum-bump!

If you still don't get signal, then it gets both nitty and gritty.

How I troubleshoot circuits is I either go back to front or front to back. Either way works for me. Front to back, I make sure the input is getting it's signal to the input on the board. I either run a signal (anything... a guitar next to you that you can strum, or a synth just oscillating away, or the output of a radio if it's all you have) into the circuit and make a "probe" by tack soldering a wire to the output jack.

Touch that wire to the point on the board where the input signal comes in.
You should hear a clean version of the signal. Now, section by section, you can go through the circuit. What I basically do is check after every transistor stage to see how far in the signal is getting. This way you can at least get a ballpark idea where the problem is.

From that point, you can check each component, starting with what you might figure to fail first. The Transistor first, maybe caps second....

Now from here on out, I have no clue.

One of the smarties around here can help you out.

Roger

[petemoore]

Solder a length of flexible wire between two alligator clips and you'll have a test lead you can just clip on/ clip off....
 repeat as necessary
 you'll need two to bypass the input and the output.

[petemoore]

of the emitter, base and collector of each transistor...see if they're reading in the range that lets them amplify.  Post those readings here.
   Iv'e never looked inside A GRBM but have heard the offbaord [all the] wires have a spotty track record...just looking andor testing with the DMM for faulty connections might turn something up.
 If it's a six lug DPDT switch, look at geo for the bypass article and get familiar with how that works, then I use the test clips make bypass of the switch right where the wires are soldereed on the lugs of the Sw.
 Usin the continuity checker of the DMM to test continuity between input [from connected guitar cable] and output to ckt [to tip of plugged in/connected  cable] when switch is in efkt position

[Greek Acrobat]

I just got it fixed. No more than a dodgy connection on the switch. Can't believe I didn't spot that just looking at it. Oh well, there it is - all dealt with now. :roll:

Cheers.

[Jered]

and if you want to learn how to do your own FX building, get into Aron's beginers project.
  Jered